Here is a page showing what is really going on - sort of. If you view the page in 12.17, it looks like the first image shown under Expected Results. If you view the page in Opera 20, it looks like the second image. So, the reason the colors would look different in Opera 20 is that 20 must be supporting only ICC version 2 color profiles and not version 4 profiles.

But as you can see in my screenshot of this page in the two browsers: it's less a ICC problem, but the colors are generally in Opera 21 not the same as in Opera 12.1 (or Firefox or Chrome -- I tried all (Windows) browsers...).

So, I still do not have an explanation for this different color matching/appereance